Abstract: A syringe for giving medical injections which has an internal mechanism for releasing and retracting a needle into the syringe after the injection has been given and retaining the needle and a hollow plunger inside the barrel of the syringe to reduce the risk of accidental needle sticks. The interior of the hollow plunger is initially hydraulically sealed off by a plunger front end wall from the fluid chamber of the syringe to prevent fluid from entering the interior of the hollow plunger. After the plunger has been depressed to expel fluid from the barrel, further depression of the plunger causes cutting punch type members to sever a disc shaped flange portion of a stem type needle retaining member and the plunger front end wall thereby permitting the spring to propel the needle and needle retaining member into the hollow plunger thereby retracting the needle and retaining member inside the barrel.